Often those people accepted for refugee status in New Zealand drop out at the last-minute due to circumstances outside their control, she said.

"Sometimes travel arrangements can't be made or there is a hitch in medical clearance. There is a constant juggle of getting the right number."

Bumping up numbers in the next refugee intake would only put undue pressure on housing and settlement services, she said.

New Zealand is one of nine countries that accommodates the bulk of refugees.

Immigration NZ general manager Stephen Dunstan said New Zealand's Refugee Quota of 750 is high relative to our population.

"There are various complicating factors that can impact on the numbers of refugees resettled in each Refugee Quota."

Health problems, such as tuberculosis, travel permits and the difficulty in getting flights can all impact the number of arriving refugees.

Factors in New Zealand can also bring the numbers down. Just 527 refugees arrived in the last financial year due to the Canterbury earthquakes. The UNHCR agreed to the lower number as emergency housing and support services were diverted to the victims of the quakes.

The government announced this year it would introduce a three-year rolling quota of refugees, so the total quota could be spread. Hayden said this would allow for better planning.

World-wide there are about 14 million recognised refugees but less than 1% are offered resettlement to a third country.